Machine with free pistons



Feb 4, 1941- R. PA'rr-:RAS PESCARA 2,230,760

MACHINE WITH FREE PIsToNs Filed May 12, 1957 2 sheets-sheet 1 llrlllrffl/g r Z 33 l c j l we@ 7 A- 15 el 37 Rau( Pahrds Bsamt mfam ,Amm

Feb. 4, 1941. R. PATERAS PESCARA 2,230,760

MACHINE WITH FREE PISTONS Filed May 12, 1937 2 Sheets-Sheet 2 /lIIllllllll/l; l,

Atturm'is Patented Feb. 4, 1'941 PATENT OFFICE MACHINE WITH FREE PIS ONS Raul Pateras Pescara, Paris, France, assignor to Socit dEtudes et de Participations, Eau, Gaz, Electricite, Energie, S. A., Geneva, Switzerland Application May 12, 1937, Serial No. 142,311

4In France May 12, 1936 I Claims.

The present invention relates to machines with free pistons, and it is especially, although not exclusively, concerned with machines of this type at least a portion of the power of which is in- 5 tended to drive at least one auxiliary receiving machine, more especially of the type having a continuous rotary movement and a gradual starting.

The object of the inventionis to provide a machine of this type which is better adapted to meet the requirements of practice.

The essential feature of the present invention consists in attaching at least one of the reciprocating parts of a machine of the type above referred to with at least one of the pumps of a hydraulic transmission system, in such manner that it is possible, through said transmission system, either to transmit to at least one receiving machine a portion of the power supplied by the free piston machine, or to transmit to this last mentioned machine energy from the outside, for instance in order to bring said reciprocating parts into a position permitting the starting of said free piston machine.

Another feature of the present invention relates more especially, although not exclusively, to free piston machines in which the speeds of the free piston or the free pistons respectively on the forward and on the back stroke are different. This feature consists, while providing a hydraulic transmission system in combination with the machine as above set forth, in constituting the motive element of this system of at least one group of two cylinder and piston devices, 35 acting respectively during the forward stroke and the back stroke of said movable parts of the engine, the two cylinders in question being made of diierent sections, and more particularly, in most cases, of sections such that both cylinder and piston devices have substantially the samemean instantaneous feed.

A third feature of the present invention consists, While associating a machine of the type above mentioned with a hydraulic transmission system, in devising said system in such manner that it ensures the braking of the driving parts of said machine at the end of their stroke, especially in the case of too long strokes of said driving parts.

Other features of the present invention will result from the following detailed description of some specific embodiments thereof.

Preferred embodiments of the present invention will be hereinafter described, with reference to (ci. fio-19) the accompanying drawings, given merely by way of example, and in which:

Fig. 1 shows, in a' diagrammatic manner, and in axial section, a free piston machine combined, according to the present invention, with a hydraulic transmission system;

Fig. 2 is a partial view of another embodiment of -some parts of said hydraulic transmission system;

Fig. 3 is a partial sectional view illustrating, in a diagrammatic manner, another embodiment of the combination of the free piston machine and the hydraulic transmission system;

Fig. 4 is a view, analogous to Fig. 3, corresponding to still another embodiment of the invention;

y Fig. 5 is a general sectional view corresponding to the two preceding figures;

Figs. 6 and 7 show two diierent positions of the transmission mechanism of Fig. 5;

Fig. 8 shows a modified form of pump.

In the following description I will consider the case of a free piston machine intended to transmit a portion of its power to the rotating parts of a receiving machine, that is to say, for instance, a water pump l, as shown by Fig. 4, a lubricating pump 2, as shown also by Fig. 4, a fan 3, as shown by Figs. 3 and 4, and so on.

Concerning first the free piston machine considered as a whole, it is made in any usual or conventional manner. For instance, as shown by the drawings, it includes two driving parts 4 and d (pistons movable in corresponding cylinders) coacting with an oscillating shaft or spindle 5 through synchronizing crank arms 6.

.As for the means for transmitting power from this machine to a receiving machine they are constructed in accordance with the following principles.

It is known, as disclosed for example in my Patent No. 2,075,133, March 30, 1937, that the driving elements of a free piston machine used for compressing gas are given reciprocating movements of freely variable stroke and that they reach their working speed nearly instantaneously as a consequence of the absence of a y-wheel.

- These characteristics render such a machine unable to be mechanically coupled with receiving machines such as those above mentioned, that ,f1

' piston machine.

, of the power previously stored up by said regu- .inders I6 and Il.

lating device.

Accordingly, concerning first said hydraulic transmission system considered in a general manner, it is devised in such manner that its motive .elements can be actuated by the reciprocating parts of the free piston machine and that its receiving elements are adapted to receive, in the form of rotary movement, 4the energy develope by said motive elements.

For this purpose, said receiving elements advantageously constitute at least one hydraulic motor of a known principle, such for instance as a gear pump or motor 'l one of the pinions of which is keyed on a shaft 8 driving the utilization machines, either through suitable kinematic connections, or, preferably, as shown by Fig. 4, directly, said machines being then keyed on said shaft 8.

Advantageously, according to the invention, the driving or motive means of the hydraulic transmission system consist of at least one pump, having at least one piston or equivalent part which is driven either directly by the reciprocating pistons of the free piston machine or through the oscillating parts of said machine. Such a pump may be given many different embodiments yand especially one of those hereinafter described by way of example with reference to the drawings.

According to the first arrangement, illustrated by Fig. 1, the motive pump of \the hydraulic transmission system includes a piston 9 cooperating, preferably with a double acting cycle, with a cylinder` I0, and provided, for instance, with inlet valves II and outlet valves I2.

This piston 9 is attached directly to the driving piston 4 through a rod I3 which further serves to guide the displacement of said piston 9.

According to the other type of arrangement above referred to', illustrated by Figs. 3 to 8, the driving or motive pump of the hydraulic transmission system includes two hollow pistons I4 and I5, rigid with each other and of the same diameter, moving respectively in opposed cyl- The flow of the liquid takes place through 'said pistons, the end of each of which is provided with an inlet valve I I', whereas the end of each cylinder is provided with a discharge valve l2. v

For the drive of said pistons, I provide a mechanism capable of transforming into a rectilinear reciprocating movement the pivoting oscillating movement of crank arms 6. Such a mechanism may be constituted, for instance, by connecting to the crank 6 oscillating around its axis 5 a shaft 5a coaxial to said axis and having a crank pin I8 on which is pivoted a slide member I9 having vertical sides adapted to coact with the corresponding sides of a slideway 20 provided in the common central body of pistons I4 and I5. Advantageously, I further provide means for guiding said pistons, said means consisting for instance of a lug 2| sliding in a. groove 22, in such manner as to avoid any possible wedging of said slide member I9 in said slideway 20.

For ensuring the fluid ltight mounting of shaft 5a in the bearing 23 of the machine frame, I 6

-may make use of any usual suitable means. For

instance,'as shown by the drawings, I provide a collar 24 applied against a packing ring 25 by a spring. In the embodiment of Fig. 3, this spring is a spiral spring 26. Preferably, as shown by Fig. 4, this spring is a leaf spring 21, which is adapted to transmit .the oscillating torque to the crankshaft IB, such an arrangement having the advantage of requiring a substantially less accurate adjustment of the whole of the transmission system with respect to the main machine.

Concerning now the regulating device to be used in combination with said hydraulic transmission system, it is mounted on the discharge conduit 28 of the driving pump.

According to a first embodiment, illustrated by Fig. 1, the excess of pressure on the output end of the pump is absorbed by an air cushion, in which case the regulating device essentially includes a fluid tight vessel 29 in which the liquid 25 can accumulate temporarily when the discharge of the driving pump is greater than the possibility of immediate absorption of the receiving pump 1.

Preferably, as shown by Fig. 2, this excess of 30 pressure is relieved by a piston 30 subjected to the opposed action of a spring 3 I, this piston being movable in a cylinder 32 mounted in shunt arrangement with respect to the discharge conduit 28. Advantageously,.a safety device is provided, consisting for instance of a short-circuiting conduit 33 the communication of which with said cylinder 32 is opened by said piston 30 when a certain limit pressure is reached on the output side of the driving pump. l

When the driving pump is of the type having two pistons such Ias shown in Figs. 3 .to 5, I prefer to use a regulating device of the type shown in Figs. 6 and 7. This device includes a diiTerential piston having a larger end 30 and a smaller end 36, this piston being urged in one direction by a spring 3Ia. A conduit 34 extends through the diiferential piston, and connects two chambers 43 which communicate with the two cylinders of the pump. The space between the pistons 30, 36 communicates with one side of the gear motor 1. There are also provided adjacent the piston 36 slots or grooves 35, so arranged that When the piston moves to the right as shown in Fig. 'I communication is established between the chamber at the right hand side and the space between the pistons in which the spring 3Ia is located.

If the delivery pressure of the pump exceeds a certain limit, the difference in pressure on pistons 30 and 36 because of the difference in their areas will move the differential piston mechanism from the position shown in Fig. 6 to that shown in Fig. 7. The slots 35 then connect the delivery chamber 43 of the pump with the space between the pistons, which space in turn is connected through opening 44 to the intake side of the pump. Therefore the gear motor'l is shortcircuited, and the pressure exerted thereon by be injurious if air, notwithstanding the packing means, should penetrate through the bearing ot shaft a to the interior of the housing 41, which.- contains the fluid oi' the hydraulic clutch mechanism.

In order to prevent penetration of air into chamber il, shaft 5a is provided with a turned portion 5b. Connected with the free space thus formed between the bearing points proper of l shaft 5a is a passage 42, which carries oi! air which tends to force through the inner bearing point of shaft 5a into the space 5b. For example,

vpassage 42 goes to an elevated receptacle 38 machine as motive uld, in which case, I advantageously provide a shunt conduit 39 on the discharge of the lubricating pump for feeding lubricant to said reservoir 38.

In all cases, I preferably arrange the various parts of the hydraulic transmission vsystem in such manner as to constitute a compact unit which is preferably iitted with cooling iins 4B located in the zone of action of the fan 3 (Figs. 3 and 4).

In this way, I provide a combination of a free piston machine with means for transmitting to various rotary receiving machines at least a portion of the power of said free piston machine, the operation of said means during the period of starting of the system taking place in the following manner:

During the period of time necessary for the receiving machine to reach its normal working speed, liquid accumulates in the chamber of the regulating device and the pressure on the output side of the driving pump increases, which has for its result to facilitate the starting of the receiving machine or machines.

In addition with the combination above mentioned, I may make use of other arrangements according to the invention, such as those hereinafter described, capable eventually of being used separately and which will be supposed, in the following description, to be applied to a system of transmission such as that above described.

It is known that in free piston machines, the forward stroke of the pistons is generally quicker than their return stroke. This may produce, in said transmission system, periodic shocks which are detrimental to the eiiciency of the transmission and of the good working of the receiving machine or machines.

In order to obviate this drawback, I make use of an arrangement according to which, instead of constituting the driving pump by two pistons of the same section, as 'shown by Fig. 5, it is made of two pistons of ldifferent respective sections, ifi and i5', the sections of these pistons being in inverse ratio to the mean forward and backward speeds oi the driving pistons of the main machine, in such manner that the smaller piston id works during the forward stroke and the larger piston i5' works during the backward stroke.

Thisl arrangement permits of obtaining mean instantaneous ows which are substantially equal for the forward and backward strokes of the pistons of the free piston machine, this corresponding to a substantial improvement of the efciency of the whole of the transmission system.

I :might of course give diiferent relative dimensions to said pistons, especially if it were desired to drive a machine or a mechanism the speed of which would vary periodically with a period equal to the period of oscillation of the driving pistons of the free piston machine.

Of course the arrangement above described could be employed for transmitting the movement of a free piston machine to a machine having a movement which is not a rotary continuous movement.

The invention also applied to the case in which the hydraulic transmission system would be used merely for setting in properv position the driving parts of a free piston machiie.

' It also applies to the case in which the intake of the pump would be kept under pressure, for instance by means of an additional pump further adapted to compensate leakage, which would permit of utilizing high pressures and reducing the space occupied by the plant.

In a general manner, while I have, in the above description, disclosed what I deem to be practical and eiiicient embodiments of the present invention, it should be well understood that I do not wish to be limited thereto as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of the present invention as comprehended within the sco-pe of the appended claims.

ysaid piston.

2. A device as in claim 1, said means for driving said pump comprising a mechanical member interconnecting said piston and pump.

3. A device as in claim 1, said pump comprising a. cylinder, a pump piston in said cylinder, and means for mechanically connecting said pump piston to said free piston.

4. A free piston compressor apparatus comprising two free pistons mounted for opposed movement in a cylinder, a linkage interconnecting said pistons to synchronize the movements thereof, a fluid pump, a rotatably operable auxiliary apparatus, hydraulic transmission means including automatic pressure regulating means for rotatably operating said auxiliary apparatus by said pump, and means for connecting said pump to said linkage for operation thereby.

5. In the combination of a free piston compressor and a pump operated thereby for driving an auxiliary apparatus through a hydraulic .transmission connecting said pump to said auxiliary apparatus; said transmission comprising `lead and return lines between said pump and apparatus, and a spring loaded differential piston interposed in said lead line for storing up a portion oi the power delivered by said pump when said power exceeds the possible power use oi said apparatus.

6. In the combination of claim 5, said diierential piston having an axial passage therein for the ilow ot liquid from said pump. and means carried by said diierential piston for.` shortcircuiting said pump for a predetermined placement of said dierential piston.

'1. A device of the character described` comprising' a free piston compressor, pump means operated by said compressor, a motor, a liquid circuit connecting said pump and motor, a liquid reservoir communicating with said circuit, a lubricating pump for said'compressor, and a conduit connecting the output of said lubricating pump with said reservoir or feeding liquid thereto.

8. In combination with a free piston comu presser including a free piston, a pump opera- 9. In combination with a free piston compressor including two pistons mounted for opposed operation and movable at dierent speeds during their respective strokes in opposite directions, a pu'mp operatively connected-to at least one of said pistons and including two pump pistons, a. motor, a liquid circuit connecting said pump to said motor, valve means for causing said pump pistons to discharge liquid successively through said circuit, and said pump pistons having individual cross sections in inverse ratio to the respective speeds of the strokes of said pistons included in said compressor 10. In the combination of a free piston compresser and a pump operated thereby `for driving an auxiliary apparatus through a hydraulic transmission connecting said pump to said auxiliary apparatus; said transmission comprising lead and return lines between said pump and apparatus, a by-pass conduit between said lines for short-cirouiting said pump, and a spring loaded piston arranged on said lead line to close, in its no position. said by-pass conduit and to open the latter upon a predetermined displacement of said piston.

RAUL PA .i 

